Compact liquid crystal display for instrument panel having a wrap around flexible printed circuit board and translucent web

ABSTRACT

A box-like molded housing with an open front has a flexible printed circuit wrapped around it, the printed circuit having a terminal array attached to a housing flange adjacent the front opening. A frame having a translucent web or filter covers the open front and contains a liquid crystal cell. A slot in the frame contains an elastomeric connector for joining terminals on the cell with terminals on the printed circuit to provide control signals to the cell. The housing interior is a reflector cavity and contains lamps for illuminating the web and the cell through the web. The printed circuit carries surface mount components, supplies power to the lamps, and has a contact array for connection to spring contacts of an external connector.

FIELD OF THE INVENTION

This invention relates to an automotive information display, and moreparticularly, to a compact package for a liquid crystal display.

BACKGROUND OF THE INVENTION

Conventional vehicle odometers comprise a mechanical device forrecording vehicle mileage which is installed on the instrument panel ofthe vehicle. These mechanical odometers tend to be bulky mechanismswhich require too much space in a very crowded environment. Toaccommodate mechanical odometers, clearance holes are typically providedin instrument panel printed circuits, and in some cases, formed deeppocket are required. The mechanical odometers are also difficult topackage and to illuminate. Since both trip odometers and total milageodometers are used, each instrument requires either two such packages ora large single package.

It is already known to employ liquid crystal displays (LCD) forinstrument panel information. These electronically driven displays havea thin liquid crystal cell and can be illuminated by variousarrangements which add bulk to the display. The various arrangementshave had differing levels of success due to the cost of the overallpackage, the quality of illumination and the ease of incorporation intothe instrument panel.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a LCD packagewhich optimizes display size, illumination, and cost, and is easy toassemble to an instrument panel. The LCD package is particularly usefulfor odometers, allowing both total milage and trip odometers to beincorporated within the same unit, and is also advantageous for otherinformation displays.

The LCD comprises a molded housing with an open front, a flexibleprinted circuit wrapped around the outside of the housing, a frame,including a light filter, mounted on the front of the housing forholding a liquid crystal cell and an elastomeric conductor for couplingthe cell and the printed circuit, and a front cover for holding theframe and liquid crystal cell to the housing.

The housing is a five-sided box providing support for the remainder ofthe components and defines an inner reflector cavity containing twolamps and having a curved back surface for uniformly illuminating thedisplay. The lamps are mounted in apertures in the printed circuit andthe bottom of the housing.

The printed circuit incorporates surface mount components, a terminalarray for supplying signals to the liquid crystal cell, conductorsconnected to the lamps, and contacts at the rear of the housing forcoupling to an external circuit.

A flange at the top of the box adjacent the open front has a pair ofalignment holes, and one end of the printed circuit containing theterminal array has similar alignment holes. Locating pins on the frameengage the holes to fasten that end of the printed circuit to thehousing. A slot within the top of the frame contains the elastomericconductor which on the rear side of the frame electrically connects tothe terminal array and on the front side of the frame connects toterminals on the liquid crystal cell to transmit control signals to thecell.

The frame has a cavity for holding the cell and locating details foraccurately positioning the cell in the cavity, including a spring fingeralong one side for biasing the cell into alignment. The frame alsoincludes a thin translucent web which diffuses light from the reflectorcavity onto the liquid crystal cell. The material may be colored toimpart color to the display.

Connection to external circuitry is accomplished by the printed circuitcontacts at the rear of the housing. A connector with spring contactscorresponding to the printed circuit contacts is mounted on an externalprinted circuit board and abuts the display for engagement of thecontacts. The connector and the housing are secured together byfasteners.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other advantages of the invention will become moreapparent from the following description taken in conjunction with theaccompanying drawings wherein like references refer to like parts andwherein:

FIG. 1 is an exploded view of a LCD, according to the invention;

FIGS. 2 and 3, respectively, are front and side views of the assembledLCD according to the invention;

FIG. 4 is a sectional view taken along line 4--4 of FIG. 3 showinghousing structure;

FIG. 5 is a sectional view taken along line 5--5 of FIG. 2 illustratingthe electrical connection to the liquid crystal cell of the display;

FIG. 6 is a partial rear view of the liquid crystal cell of the displayshowing terminals connections; and

FIG. 7 is an exploded view of an external connector and the rear of theLCD, according to the invention.

DESCRIPTION OF THE INVENTION

Referring first to FIGS. 1-4, a liquid crystal display package 10 has amolded housing 12 as its base structural member, the inside of thehousing serving as a light reflecting cavity. The housing 12 is afive-sided box having a top wall 14, a rear wall 16, a bottom wall 18,two end walls 20, and a front opening 22. The rear wall 16 is curveddefining two cylindrical sections serving as internal concave lightreflectors 24. Spacer pins 26 extend rearwardly from each corner of therear wall 16.

A pair of lugs 27 just inboard of the end walls extend rearwardly tofacilitate connection to an external connector. An upper flange 28extending upwardly from the top wall 14 adjacent the front opening 22has an alignment hole 30 at each side. Side flanges 32 extend laterallyfrom the end walls 20 adjacent the opening 22 and terminate in tabs 34.Apertures 36 in the bottom wall 18 centered relative to the lightreflectors 24 permit the insertion of lamps 38 for illuminating thecavity.

A flexible printed circuit 40 is wrapped around the housing 12, coveringthe top flange 28, the top wall 14, the rear wall 16 and the bottom wall18. The printed circuit has at one end a pair of alignment holes 42corresponding to the hole 30 in the top flange 28, and a terminal array44 between the holes 42 for carrying liquid crystal control signals. Theprinted circuit has conductors, not shown, comprising the displaycircuit along with surface mount logic module 46 which generates controlsignals for the display, and other surface mount components 48.

Apertures 50 in the other end on the printed circuit align with housingapertures 36 for the lamps 38, and circuit conductors supply the lamps38. Rear apertures 52 accommodate the lugs 27. A row of contacts 54forming a contact array on the printed circuit at the back of thehousing (FIG. 7) permit connection to external circuitry which suppliespower and information or data to be displayed.

The printed circuit extends from the top of the flange 28 to the rear ofthe top wall 14 at an angle which leaves a space between the circuit andthe wall. A self-stick gasket 56 is secured to the top wall 14 justunderneath the printed circuit to fill the space and provide backing forthe printed circuit and the logic module 46 which is located there.

A molded filter or frame 60 has a peripheral rectangular structure forseating against the flanges 32 of the housing and against the terminalarray 44 which covers the flange 28. Locator pins 62 extend rearwardlythrough the alignment holes 30, 42 to secure the printed circuit to theflange 28 and accurately position the terminal strip relative to theframe. The rear wall of the frame 60 comprises a translucent web 64, thewhole frame being molded of a translucent polycarbonate which is coloredto filter the light if a colored display is desired. Forward of the web64, the frame defines a recess for snugly receiving a liquid crystalcell 66.

One end of the frame has locating stops 68 for precisely positioning thecell 66 laterally, and the opposite end of the frame has a spring finger70 biased laterally inwardly for urging the cell 66 against the locatingstops 68. The top member 72 of the frame, best shown in FIG. 5, has aslot 74 extending along its length contiguous with the terminal array44. The slot 74 contains an elastomeric connector 76 which extendsbeyond the limits of the frame to securely contact the terminal array 44and the corresponding terminals 78 (FIG. 6) on the cell 66. Theelastomeric connector 76 has alternate conducting and insulatingstriations which make electrical contact between corresponding terminalelements of the array 44 and the cell 66.

An outer metal cover 80 has a margin 82 covering the boundaries of theframe 60 and the cell 66 and defining a window for viewing the cell. Thecover 80 has lateral spring fingers 84 reaching to the housing to lockonto the tabs 34 on the side flanges 32, thereby holding the assemblytogether. The force of the cover against the cell and the frame causesthe elastomeric connector 76 to be compressed to assure tight engagementwith the terminals. The sides of the slot contain the elastomericconnector against collapse, assuring transmission of the force throughthe connector.

The display is assembled by placing the cover 80 into a holding fixture,inserting the liquid crystal cell 66 into the frame 60 and placing theframe/cell assembly into the cover. Then the elastomeric connector 76 isinserted into the slot 74. The alignment holes 42 of the printed circuitare placed over the locator pins 62 of the frame, the gasket 56 isattached to the housing, the alignment holes 30 of the top flange 28 arepositioned over the locator pins 62 and the housing 12 is snapped intothe cover 80. The loose end of the printed circuit is pulled around thehousing, a hole in the circuit is placed over a pin on the bottom wall18 to temporarily hold the circuit, and then the two lamps 38 areinstalled, thus finally securing the circuit to the housing.

While the drawing shows two rows of digits on the display to accommodatetwo odometer displays, it will be apparent that other arrangements arereadily implemented, according to the desired display implementation.The digits will be adequately and uniformly illuminated due to the useof the filter web 64 to diffuse the light, the two lamps to directlylight the web and the reflective shaped cavity to indirectly light theweb.

As shown in FIG. 7, an external connector 90, installed on a flexible ora hardboard printed circuit 92, has a base 94 for contact at its cornerswith the spacers 26 on the back of the housing, and two holes, notshown, surrounded by counterbores 96 for registry with the lugs 27. Whenthe connector 90 is installed on the display 10, a row of springcontacts 98 on the connector 90 engage the contacts 54 on the printedcircuit 40.

A raised pad 100 molded on the back of the housing backs up the circuitin that location to resist the force of the spring contacts on theflexible printed circuit. Screws, not shown, are inserted through theholes and into the lugs 27 of the housing to secure the installation.

The LCD package is thus capable of being made very small, especiallydepth-wise, while assuring good illumination of the liquid crystal cell.The package is easily assembled with the parts accurately aligned forproper and secure electrical coupling. The small depth and the ease ofcoupling to an external connector facilitate its incorporation andassembly into an instrument panel.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A liquid crystal displayfor mounting in an automotive vehicle comprising:a molded box-likehousing having a front opening and a flange along at least a portion ofthe front opening; a flexible printed circuit wrapped around the box andhaving a terminal array positioned on the flange; electrical componentsmounted on the printed circuit for supplying control signals to theterminal array; a liquid crystal cell having a plurality of contact padsand mounted over the front opening; illumination means within thehousing for backlighting the liquid crystal cell; a frame for supportingthe cell and having means for registration with the housing and theprinted circuit to align the contact pads of the cell with the terminalarray; a translucent web within the frame between the cell and thehousing and covering the front opening for passing light from theillumination means to the cell; and means in the frame for coupling thecontact pads with the terminal array, whereby the liquid crystal cellreceives the control signals.
 2. The invention as defined in claim 1,wherein the means in the frame for coupling the contact pads with theterminal array includes:a slot in the frame contiguous with the contactpads and the terminal array; and an elastomeric connector in the slot inelectrical contact with and interconnecting the contact pads and theterminal array.
 3. The invention as defined in claim 2 furtherincluding:an outer clamp member secured to the housing and urging theframe and the cell toward the housing, thereby compressing theelastomeric connector between the terminal array and the cell, andclamping the terminal array portion of the printed circuit against thehousing.
 4. A liquid crystal display for mounting in an automotivevehicle comprising:a molded box-like housing having a front opening anda flange along at least a portion of the front opening; a flexibleprinted circuit wrapped around the box and having a terminal arraypositioned on the flange; electrical components mounted on the printedcircuit for supplying control signals to the terminal array; a liquidcrystal cell mounted over the front opening and coupled to the terminalarray for receiving the control signals; and illumination means withinthe housing for backlighting the liquid crystal cell; wherein the flangehas registration holes, and the display includes a frame for holding thecell adjacent the opening; the frame including: locating pins extendingthrough the registration holes; a translucent web covering the frontopening and admitting light from the illumination means to the cell;lateral stops at one side of the frame for positioning the cell in theframe; and a laterally biased spring finger at the opposite side of theframe for urging the cell against the stops.